1. Field of the Invention
The present invention relates to a circuit and a method, and in particular to a circuit for improving the speed of read operations in a memory and to a method of performing the same.
2. Discussion of the Related Art
FIG. 1 illustrates a portion 100 of a memory device comprising complementary bit lines BL and  BL, and memory cells 102A, 102B coupled to bit line BL via corresponding transistors 104A and 104B, and to bit line  BL via corresponding transistors 106A and 106B. When the memory cell 102A or 102B is to be read, the bit lines BL and  BL are, for example, precharged with a high voltage level, and then the corresponding transistors 104A, 106A or 104B, 106B are activated by a corresponding control signal SA, SB at their gate nodes. Depending on the bit value stored in the memory cell, the voltage on one or the other of the bit lines BL,  BL will drop. Read circuitry 108 detects this voltage drop, and outputs the corresponding data D0.
A common objective of such memory devices is to be able to perform relatively high speed memory read operations, in order to allow high read data rates from the memory. The speed of the read operation can be limited by the speed at which the voltage on the bit line BL or  BL drops once the memory cell to be read has been coupled to the bit lines.
A further common objective of such memory devices is to provide high energy efficiency. One solution that has been proposed is the use of low or ultra low supply voltages, which reduce current consumption in the device.
However, the use of low supply voltages may have two main drawbacks. First, it can slow down the discharge of the bit lines during read operations, and thus reduces the speed of the read operations. Second, due to the lowered ratio between the dynamic and the leakage currents at low supply voltages, the voltage drop on BL and  BL induced by the leakage from the memories that are not being read can be erroneously interpreted as a legitimate drop, leading to a read error due to the fact that the voltage drop on both lines BL and  BL will be detected as dropping.